Photolithography systems are known in the art that direct light beams onto a photosensitive surface covered by a mask, etching a desired pattern on the substrate corresponding to the void areas of the mask. Maskless photolithography systems are also known in the art as described in Singh-Gasson, Sangeet et al., Nature Biotechnology 17, 974-78, 1999. The system described in this article uses an off-axis light source coupled with a digital micromirror array to fabricate DNA chips containing probes for genes or other solid phase combinatorial chemistry to be performed in high-density microarrays.
A number of patents also exist which relate to maskless photolithography systems, including U.S. Pat. Nos. 5,870,176; 6,060,224; 6,177,980; and 6,251,550; all ofwhich are incorporated herein by reference. While maskless photolithography systems disclosed in the art are directed to DNA chip and semiconductor manufacture, these prior art systems and methods notably lack reference to other applications lending themselves to maskless photolithography techniques.
Photo-assisted wet etching of various semiconductor materials has been disclosed [Shockley et al., U.S. Pat. No. 3,096,262; T. Yoshida et al., Proc IEEE Mems., 56-61, 1992; B. Peters et al., 7th Intl. Conf. On Solid State Sensors and Actuators (Transducers '93), 254-57, 1993; c. Youtsey et al., Appl. Phys. Lett. 71(15), 1997]. In these references, the patterns generated are defined by physical masks placed in the path of light used for photo-activation. While use of wet etching techniques simplifies manufacture of semiconductors by eliminated the requirement of clean rooms required by traditional semiconductor manufacturing techniques, physical masks are still required in the process. While effective, the use of physical masks in the wet etching process has numerous drawbacks, including the cost of fabricating masks, the time required to produce the sets of masks needed to fabricate semiconductors, the diffraction effects resulting from light from a light source being diffracted from opaque portions of the mask, registration errors during mask alignment for multilevel patterns, color centers formed in the mask substrate, defects in the mask, the necessity for periodic cleaning and the deterioration of the mask as a consequence of continuous cleaning. Thus, the drawbacks of using masks are not eliminated in the prior art wet etching techniques.
Patterns and structures are known to be created in photosensitive glass, such as with the use of a direct laser writing process (C. Gimkiewicz et al., Microsystems Technology 4, 40-45, 1997). It is also known to use a hard physical blocking mask-to-mask ultraviolet (UV) exposure to glass (R. Salim et al., Microsystems Technology 4, 32-34, 1997). However, the laser process requires an expensive laser system and associated electronic controls and can produce objectionable waste material during the laser etching process. On the other hand, the UV system disclosed in Microsystems Technology eliminates the need for a laser, but still requires the use of masks. Thus, the disadvantages of using masks are not eliminated.
Further, it is also known to make printed metal patterns by etching away unwanted material from a substrate. However, this process can create hazardous waste material that requires special handling for disposal. In addition, the process is inefficient due to loss through waste and expensive reclamation efforts.
Photo-selective metal deposition was introduced by Western Electric, Incorporated in a factory setting in the 1960's. In the Western Electric technology, a photofilm having a pattern thereon was placed on a drum having a light source in its center. However, the film had to be changed to create different patterns, and thereby, this system suffers from the same drawbacks as other mask-type photolithography systems.
Accordingly, there is a need in the art for a method and system for maskless photolithography to create 2-D and 3-D patterns on objects using etching and deposition techniques. Specifically, the method and system needs to provide a maskless photolithography system for wet etching, creation of designs in photosensitive glass, and metal deposition processes. This system needs to combine ease of use, reconfigurability, and the ability to eliminate the need for the use of physical masks. In summary, the system needs to provide all the advantages of a maskless photolithography system at a reasonable cost, and include capabilities tailored to specific applications.